An endoscope, comprising: an elongated member defining an inflow channel and configured to accept an instrument inserted therethrough and a valve assembly coupled to a proximal end of the elongated member and including: (i) a valve housing having a resector inlet, a valve inlet in fluid communication with a fluid source, and a valve outlet coupled to the elongated member and in fluid communication with the inflow channel, and (ii) a valve body rotatable within the valve housing between the valve inlet and the valve outlet to regulate an impedance of fluid flow through the endoscope, the valve body defining a throughbore and a blind bore, wherein, in a first position of the valve body, the throughbore is aligned with the valve inlet and the blind bore is aligned with the valve outlet, and, in a second position of the valve body, the throughbore is aligned with the valve outlet and resector inlet, and the blind bore is aligned with the valve inlet, and wherein a first impedance of fluid flow through the valve housing with the valve body in the first position is substantially equal to a second impedance of fluid flow through the valve housing with the valve body in the second position and with a resector extending into the resector inlet, through the throughbore, and into the inflow channel of the elongated member.
